Remove use-toast.tsx, refactor auth methods, and update UI components

This commit removes the redundant `use-toast.tsx` file and refactors the authentication methods in `personal-accounts-server-actions.ts` to enhance service integration and data handling. UI components like `LanguageDropdownSwitcher` and `site-header-account-section.tsx` have been refined for better readability. Changes in the `config.tsx` file aim to improve the overall code cleanliness. The `schema.sql` file under migrations was updated to cascade delete for 'invited_by' reference.

packages/features/accounts/src/server/services/personal-accounts.service.ts

@@ -13,5 +13,10 @@ import { Database } from '@kit/supabase/database';
 export class PersonalAccountsService {
   constructor(private readonly client: SupabaseClient<Database>) {}
 
-  async deletePersonalAccount(param: { userId: string }) {}
+  async deletePersonalAccount(
+    adminClient: SupabaseClient<Database>,
+    params: { userId: string },
+  ) {
+    return adminClient.auth.admin.deleteUser(params.userId);
+  }
 }